Stabilisation of flavors

ABSTRACT

Volatile flavour molecules having a particular cyclic enolone structure are stabilised by complexation with alkaline earth metal ions. These complexes are stable until exposed to certain conditions of temperature and/or moisture.

BACKGROUND OF THE INVENTION CROSS-REFERENCE TO RELATED APPLICATION

This application is a national stage application filed under 35 USC 371of PCT/GB96/01028.

1. Field of the Invention

The subject invention relates to the stabilisation of flavours.

2. Brief Description of Related Art

It is well known to enhance the flavour and/or aroma of tobacco (ortobacco smoke) and foodstuffs, and a variety of flavourants have beendeveloped for such purposes. Examples of commonly used flavourantsinclude vanillin and menthol and derivatives thereof. It would bedesirable to use as flavourants other compounds including furaneol andcyclotene. However, these latter compounds have a high volatility andare often unstable in their standard form. Therefore it is not practicalto use these compounds in products as this will result in, for example,a reduced shelf-life of the product due to volatilisation of thecompound during storage.

There have been many attempts to provide means whereby volatileflavourants are prevented from volatilising at ambient temperatures andreleased only when exposed to high temperatures. One example of such anattempt is the stabilisation of a flavour molecule by the formation of acomplex, wherein the flavourant forms an inclusion complex with a "host"compound. This method of stabilisation is illustrated by U.S. Pat. No.3,047,431, U.S. Pat. No. 3,288,146 and EP 0 503 795 A2. Formation of aninclusion complex involves the host compound forming around the guest(flavour) molecule. The Van der Waals forces which form between the hostmolecule and the guest molecule cause a reduction of energy in theinclusion complex and therefore the flavour is stabilised. Adisadvantage of this method of stabilisation is that in a mixture ofdifferent flavour molecules, certain molecules may be stabilised inpreference to others depending upon the structure of the host and guestmolecules.

Another method of stabilising flavourants is to encapsulate the flavourmolecules in such a manner that they are not released from the capsuleunless subjected to either heat or pressure. This method ofstabilisation is taught in U.S. Pat. No. 3,162,199 and U.S. Pat. No.3,550,598. This method of stabilisation is not specific and can be usedto stabilise all types of flavourants.

Both of the above methods of stabilising flavours involve a physicalrestriction of the molecules. In effect the flavourant is held in asurrounding structure until the flavourant is released by exposure ofthe structure to certain conditions. There is no chemical reactionbetween the flavourant and the stabilising compound in either case.

The subject invention provides an alternative mode of stabilisation,which alternative mode involves chemical reaction with the flavourant.

An article published in the Journal of Organic Chemistry in 1993 atpages 7557-7561 describes development work for the purpose of improvingmethods of purification of phenacyl alcohol using calcium complexation.The subject matter of the article is to be considered as incorporatedherein.

SUMMARY OF THE INVENTION

The subject invention provides a stable flavour complex comprising analkaline earth metal ion and two cyclic molecules, wherein for each ofsaid molecules the cyclic ring thereof comprises first and secondfunctional groups, which functional groups are located at adjacentpositions of the cyclic ring, each of which functional groups provides abond with said ion, said cyclic ring further comprises a double bond,which double bond is in conjugated relationship with said secondfunctional group, and one at least of said cyclic molecules being aflavour molecule.

BREIF DESCRIPTION OF THE DRAWINGS

The drawing is a structural representation of a complex of theinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Preferably both of the cyclic molecules of the flavour complex aremolecules of a flavour compound.

Preferably the alkaline earth metal ion is a calcium ion. The alkalineearth metal ion is suitably provided by a water soluble salt. A suitablecalcium salt is CaCl₂, and is advantageously anhydrous CaCl₂.

The subject invention further provides a method of producing a stableflavour complex, wherein an alkaline earth metal salt and a cyclicflavour compound, are reacted together in solution, said stable flavourcomplex being extracted from the reaction mixture by means of aseparation technique, the cyclic molecules comprising first and secondfunctional groups, which functional groups are located at adjacentpositions of the cyclic ring, and the ring of each cyclic moleculefurther comprising a double bond in a conjugated relationship with saidsecond functional group.

It is envisaged that a non-flavour cyclic compound may additionally bepresent in the reaction mixture.

The alkaline earth metal salt is preferably a soluble salt and is,suitably, a water soluble salt, for example calcium chloride.Advantageously the salt is in the form of an anhydrous salt.

Preferably, the reaction between the alkaline earth metal salt and thecyclic compound takes place under reflux conditions.

Suitable solvents providing the solution required for reflux includeboth protic solvents, e.g., ethanol, and aprotic solvents, e.g.tetrachloromethane. Preferably the solvent is dried (dehydrated) priorto reaction. Particularly suitable solvents include absolute ethanol andabsolute methanol.

The cyclic molecules may be heterocyclic molecules or homocyclicmolecules.

The first functional group comprises either an alcohol group or a thiolgroup.

The second functional group preferably comprises either doubly bondedoxygen or doubly bonded sulphur.

If the cyclic molecule is a heterocyclic molecule, the heterocyclic ringmay contain oxygen, sulphur or nitrogen or derivatives of nitrogen.

The cyclic ring may also comprise side chains, for example, of alkylgroups or alkyl derivatives.

Suitable heterocyclic compounds include, furaneol, nor-furaneol, maltol,iso maltol, ethyl maltol and maple lactone.

A suitable homocyclic molecule is cyclotene.

Complexation occurs because of the nature of the methyl enoloneconfiguration. Consider, for example, furaneol as the flavour compoundreacting with ionic calcium chloride. The hydrogen of the alcohol groupof the furaneol is constantly moving between the oxygen of the alcoholgroup and the oxygen of the ketone group. This corresponds with thesimultaneous movement of the electrons of the oxygen double bond betweenthe ketone group and the alcohol group. When the cyclic molecule comesinto contact with the ionic calcium the hydrogen of the alcohol group ofthe cyclic molecule is displaced and dative bonds form between thecalcium ion and the oxygen atoms of each of ketone and alcohol groups ofthe flavour compound, thereby stabilising the flavour compound. Thedouble positive charge of the calcium ion means that each calcium ioncan stabilise two cyclic molecules. Therefore, the complex preferablycomprises a calcium ion between two cyclic molecules, as shown in FIG.1.

If the two cyclic molecules in a complex are both flavour molecules, thetwo flavour molecules may be either two of the same flavour molecules ortwo different flavour molecules. The particular identity of the flavourmolecules of the complex, and the combination thereof, will determinethe flavour and/or aroma properties released upon exposure of thestabilised flavour complex to moisture and/or heat. For example, if theflavour molecules contain no nitrogen or sulphur then the flavourproduced will be sweet. Complexes as per the subject invention may havearomas/flavours of coffee, bread or meat products, for example.

A first stabilised flavour complex comprising two of the same flavourmolecules, and a second stabilised flavour complex also comprising twoof the same flavour molecules, the second stabilised flavour complexcomprising different flavour molecules from that of the first stabilisedflavour complex, may be mixed to produce a specific flavour/aroma whichwill be released upon exposure to moisture and/or heat.

A stabilised flavour complex according to the present invention may beincorporated into a smoking article. For example, the complex may beincorporated into the filter, the tobacco blend or applied to thewrapper of the smoking article. The method of incorporation may proceedaccording to any suitable method known in the art.

A stabilised flavour complex according to the present invention may alsobe applied to or incorporated in dehydrated foodstuffs or beverages;examples are meat products and coffee. The complex is suitably appliedto/incorporated in microwaveable meat products such as beefburgers,wherein the flavour/aroma will be released upon cooking, and instantcoffee, wherein the flavour/aroma will be released upon contact withboiling water. Complexes of the subject invention are particularlyuseful in applications where a roasted or toasted flavour/aroma isrequired upon cooking. The method of incorporation of the stabilisedflavour complex in the foodstuff/beverage will vary depending upon thenature of the foodstuff/beverage and any suitable method known in theart may be employed.

An advantage of the flavour complex stabilised in accordance with thesubject invention when incorporated into a smoking article is that theflavour/aroma will not be released until the product is exposed tomoisture and/or heat, i.e. upon smoking of, for example, a cigarette.

Another advantage of the invention resides in the fact that thestabilised molecules are not only stabilised in the respect that theyare less volatile, but the molecules are also stabilised in the sensethat they will not react with compounds in the material in which theyare incorporated.

Stabilisation of flavour compounds as described with respect to thesubject invention also prevents ring opening reactions of the flavourmolecules.

The following examples are further illustrative of the subjectinvention. The specific ingredients and process parameters are presentedas being typical, and various modifications can be derived in view ofthe foregoing disclosure.

EXAMPLE 1

Maltol was refluxed in anhydrous absolute ethanol for four hours in thepresence of anhydrous calcium chloride. The ratio of anhydrous calciumchloride to maltol was 1:2. After reflux the reaction mixture wasconcentrated to about a quarter of the original volume by bubblingnitrogen gas through the surface of the mixture. In order to separateout the product, pentane was added to the concentrated reaction mixture.The volume of pentane added to the reaction mixture was approximatelyequal to the volume of the concentrated reaction mixture. The mixturewas left to cool for about twelve hours at around 4° C., whereby theproduct crystallised out from the reaction mixture. The crystallineproduct was filtered and stored in a desicator.

EXAMPLE 2

Cyclotene was processed substantially according to the procedure givenin Example 1. However, in this case, the reaction mixture wasconcentrated until it was almost dry. Pentane was then added as inExample 1. The mixture was left to cool at 4° C. for in excess of twelvehours.

An alternative method of crystallisation involves drying out thereaction mixture followed by re-dissolving in a small amount of a 1 to 1mixture of ethanol and pentane. Crystallisation will occur when themixture is left to stand at around 4° C.

We claim:
 1. A stable flavour complex, comprising an alkaline earthmetal ion and two cyclic molecules, wherein for each of said moleculesthe cyclic ring thereof comprises first and second functional groups,which functional groups are located at adjacent positions of the cyclicring each of which functional groups provides a bond with said ion, saidcyclic ring further comprises a double bond in a conjugated relationshipwith said second functional group, and one at least of said cyclicmolecules being a flavour molecule, said flavour molecule being releasedupon exposure of said flavour complex to moisture and/or heat.
 2. Acomplex as claimed in claim 1, wherein said two cyclic molecules areboth flavour molecules.
 3. A complex as claimed in claim 2, wherein thetwo flavour molecules are two different flavour molecules.
 4. A complexas claimed in any one of claims 1, wherein said first functional groupcomprises either an alcohol group or a thiol group.
 5. A complex asclaimed in claim 1, wherein said second functional group compriseseither doubly bonded oxygen or doubly bonded sulphur.
 6. A complex asclaimed in claim 1, wherein the cyclic ring comprises side chains ofalkyl groups or alkyl derivatives.
 7. A complex as claimed in claim 1,wherein said cyclic molecule is a heterocyclic molecule and saidheterocyclic ring comprises oxygen, sulphur, nitrogen or nitrogenderivatives.
 8. A complex as claimed in claim 7, wherein saidheterocyclic molecule is any one or more selected from the groupconsisting of furaneol, nor furaneol, maltol, iso maltol, ethyl maltoland maple lactone.
 9. A complex as claimed in claim 1, wherein saidcyclic molecule is cyclotene.
 10. A complex as claimed in claim 1,wherein said alkaline earth metal ion is a calcium ion.
 11. A complex asclaimed in claim 1 wherein the alkaline earth metal ion is in the formof a water soluble salt.
 12. A complex as claimed in claim 11, whereinthe alkaline earth metal salt is anhydrous calcium chloride.
 13. Amethod of stabilising volatile flavour compounds, wherein an alkalineearth metal ion and two volatile cyclic molecules, are reacted togetherin solution, at least one of said cyclic molecules being a flavourmolecule, a stable flavour complex being extracted from the reactionmixture by means of a separation technique, said cyclic moleculescomprising first and second functional groups, which functional groupsare located at adjacent positions of the cyclic ring, and said ring ofeach cyclic molecule further comprising a double bond in a conjugatedrelationship with said second functional group and said flavour moleculebeing released upon exposure of said flavour complex to moisture and/orheat.
 14. A method as claimed in claim 13, wherein said flavourcompound, comprises any one or more of the group consisting ofcyclotene, maltol, iso maltol, furaneol, maple lactone and nor furaneol.15. A method as claimed in claim 13, wherein said cyclic molecules are amixture of flavour molecules and non-flavour molecules.
 16. A method asclaimed in claims 13, wherein said cyclic molecules are a mixture of twodifferent flavour compounds.
 17. A method as claimed in claim 13,wherein said alkaline earth metal salt and said cyclic molecules are inanhydrous solution.
 18. A method as claimed in claim 13, wherein. a.suitable solvent is absolute ethanol or absolute methanol.
 19. A smokingarticle comprising a stable flavour complex, said stable flavour complexbeing as claimed in claims
 1. 20. A foodstuff comprising a stableflavour complex, said stable flavour complex being as claimed inclaim
 1. 21. A beverage comprisng a stable flavour complex, said stableflavour complex being as claimed in claim 1.